Specialized mass spectrometry analyses are provided to the laboratory and to other collaborating units. The emphasis of this work is split between identification of trace organic compounds isolated from biological sources and the mass spectrometry of biopolymers (e.g. peptides, proteins and oligonucleotide). A very close working relationship and collaboration is maintained with the Laboratory of Biophysical Chemistry, NHLBI, especially with the research into, and use of techniques for, mass spectrometry of macromolecules. While a large number of analyses are performed to assist others in their research (total analyses for current year were 3030 on the SX102 and approx. 1500 by MALDI), as much emphasis as possible is placed on mass spectrometry technique related research. Major research accomplishments have involved the development of a method to allow the first spectra of intact double-stranded and triple-stranded DNA by matrix assisted laser desorption mass spectrometry to be observed, and the identification of the disulfide bonds in three proteins. In one of the proteins, a method was developed which allowed for the identification of the cross-linking using the combined information from the many fragments formed under acid hydrolysis. Techniques for the location and identification of other post-translational modifications are under development. In collaboration with the National Institute of Standards and Technology (NIST), mass spectra of over 2400 compounds, the structures of which had been elucidated at NIH, the Walter Reed Army Institute of Research and other government agencies, have been obtained and processed for introduction to the NIST mass spectra library database. During the year, the JEOL SX102 mass spectrometer, on which most of the analyses are performed, was upgraded with a new data system and electrospray source. This has greatly enhanced the group's ability to perform biopolymer mass spectrometry analyses.